When you setup cross-save, you selected your Xbox account as the active save data. This would be why you cannot access your Steam characters. Please read through the article linked below, and fill out the contact form at the bottom. Request that your active save be changed from Xbox to Steam, and Bungie staff may assist, at their discretion. Please note that these forms are reviewed during regular business hours only (9am to 5pm Pacific, M-F), so it may take a few days to receive a response. https://www.bungie.net/en/Help/Troubleshoot?oid=48099